Once you cancel the subscription, you cannot perform any future refund or proration actions
You can reactivate canceled subscriptions. This action also enables actions such as proration, refunds, renewals and upgrades.
To cancel a subscription, click the Cancel immediately button from the subscription page. Choose whether to notify the customer about the subscription cancellation, by checking the "Send notification email to customer" checkbox. Leave the option unchecked in case you don't want your customers to be notified about the cancellation.